A control relay board used in a motor train unit employs the structure of a mother board and daughter boards. Both of the mother board and the daughter boards employ circuit boards for layout. Elements such as relays, diodes are arranged on the daughter boards, and the daughter boards are connected to the mother board by connectors. A pressure plate structure is adopted to press the daughter boards on a frame of the control relay board uniformly. A time relay and other elements are arranged on a board surface of the control relay board. Routes of the elements arranged on the board face and routes of the mother board are all connected by the connectors on the board surface, and the connectors are external electric interfaces of the control relay board.
The pressure plate structure of the control relay board of this type has some deficiencies. The pressure plate structure and the daughter boards are apt to be deformed, and the daughter boards are apt to be caused to loosen, thereby resulting in electric system faults, therefore the pressure plate structure cannot meet the requirements of industrialized electric equipment.